The present invention relates to a scroll compressor and an air conditioner, and more specifically, it relates to a scroll compressor and an air conditioner capable of controlling switching between unloaded operation and full-loaded operation, controlling the capacity of refrigerant injection and controlling the rotational frequency of a motor on the basis of a result of detection of the operating state.
FIG. 17 shows an exemplary conventional refrigerant compressor. This compressor is disclosed in Japanese Patent Laying-Open No. 11-182479 (1999).
As shown in FIG. 17, the refrigerant compressor comprises a closed container 63 having a fixed scroll 56 and a rocking scroll (not shown) built therein. A cylinder 53 is formed on an end of the closed container 63. A piston control valve 51 and a compression spring 52 are set in the cylinder 53.
The cylinder 53 is further provided with a first passage 60 communicating with an intermediate pressure space 59, a second passage 61 communicating with a suction pressure space 57 and a third passage 62 communicating with a discharge pressure space 58 through a discharge port 55. A back pressure space 54 of the piston control valve 51 communicates with the third passage 62.
In the compressor having the aforementioned structure, the piston control valve 51 moves in response to the difference between a suction pressure (Ps) and a discharge pressure (Pd) for a refrigerant to open/close the first passage 60. Thus, the operating state of the compressor is switched between operation (full-loaded operation) closing the first passage 60 for attaining discharge capacity of 100% and operation (unloaded operation) opening the first passage 60 for reducing the discharge capacity.
The aforementioned compressor, automatically controlling switching between unloaded operation and full-loaded operation in response to the pressure condition in the compressor, has the following problem. This problem is now described with reference to FIG. 18. FIG. 18 illustrates the relation between a condensing temperature (Tc), an evaporating temperature (Te) and an operating pressure ratio (Pr).
When the evaporating temperature (Te) is low and the condensing temperature (Tc) is high (the region shown by slanting lines in FIG. 18) while required refrigerating ability is small in a refrigerating cycle, for example, the aforementioned compressor is not subjected to unloaded operation. This is because the suction pressure (Ps) for the refrigerant is reduced and the discharge pressure (Pd) is increased when the evaporating temperature (Te) is low and the condensing temperature (Tc) is high, to close the aforementioned first passage 60.
When not subjected to unloaded operation but operated with small ability as described above, the compressor must unavoidably be operated at a low pressure with difficulty in lubrication. In such low-speed operation, further, motor efficiency is lower than that in intermediate- or high-speed operation, and efficiency may be reduced due to leakage of compression gas in the compressor or the like.
As hereinabove described, the conventional compressor automatically controls switching between unloaded operation and full-loaded operation without detecting the operating state. Therefore, the compressor cannot sometimes be properly and efficiently operated in response to the operating state. This problem can also arise in an air conditioner comprising the aforementioned compressor.
The present invention has been proposed in order to solve the aforementioned problem. An object of the present invention is to provide a scroll compressor and an air conditioner capable of selecting proper and efficient operation in response to every operating state.
A scroll compressor according to the present invention has a movable scroll (2) and a fixed scroll (1) forming a compression chamber (40) compressing a refrigerant, and comprises a variable-speed motor (28), capacity control means (12, 35), an operating state detection part (27) and a control part (26). The variable-speed motor (28) drives the movable scroll (2). The capacity control means (12, 35) controls the capacity of the scroll compressor by supplying the refrigerant into the compression chamber (40) or bypassing the refrigerant from the compression chamber (40) to a low-pressure side. The operating state detection part (27) detects the operating state of the scroll compressor. The control part (26) controls operation of the capacity control means (12, 35) and the rotational frequency of the motor (28) in response to the operating state detected by the operating state detection part (27).
The scroll compressor comprises the aforementioned operating state detection part (27), so that the operating state of the scroll compressor can be detected. Further, the scroll compressor comprises the aforementioned control part (26), so that the operation of the capacity control means (12, 35) and the rotational frequency of the motor (28) can be controlled in response to the operating state of the scroll compressor. Thus, proper and efficient operation can be selected under every operating condition. The aforementioned operating state detection part (27) and control part (26) may be set not only in the compressor but also in a refrigerating/air conditioner system.
In the scroll compressor according to the present invention, the operating state detection part (27) preferably includes an operating pressure ratio detection part detecting an operating pressure ratio indicating the value of the ratio of a suction pressure for the refrigerant to a discharge pressure for the refrigerant and a required ability detection part detecting required ability in operation of the scroll compressor, and the control part (26) preferably controls the operation of the capacity control means (12, 35) and the rotational frequency of the motor (28) in response to the aforementioned operating pressure ratio and required ability.
The operating state detection part (27) has the operating pressure detection part and the required ability detection part as hereinabove described, whereby the operating state of the scroll compressor such as the operating pressure ratio or the required ability can be detected. The control part (26) controls the operation of the capacity control means (12, 35) and the rotational frequency of the motor (28) in response to the operating pressure ratio and the required ability detected in the aforementioned manner, so that the scroll compressor can be operated in high efficiency under every operating condition.
In the scroll compressor according to the present invention, the capacity control means (12, 35) preferably includes unloading means (12) for substantially delaying a compression starting point in the compression chamber (40) and performing unloaded operation.
The capacity control means (12, 35) can be exemplified by the unloading means (12). When the scroll compressor comprises the unloading means (12), the unloading means (12) can be intentionally operated in response to the operating state of the scroll compressor for performing unloaded operation. More specifically, the unloading means (12) can be intentionally operated for performing unloaded operation under conditions of a low evaporating temperature, a high condensing temperature and small required refrigerating ability, for example. Thus, it is possible to avoid the general problem of low-speed operation with difficulty in lubrication.
In the scroll compressor according to the present invention, the capacity control means (12, 35) includes refrigerant injection means (35) for injecting the refrigerant into the compression chamber (40).
The capacity control means (12, 35) can alternatively be exemplified by the refrigerant injection means (35). When the scroll compressor comprises the refrigerant injection means (35), the injection means (35) can be properly operated in response to the operating state of the scroll compressor and the capacity of the scroll compressor can be increased. Thus, the variable ability width of the scroll compressor can be increased. When employing the refrigerant injection means (35) along with the aforementioned unloading means (12), the control part (26) can control the operation of the unloading means (12) not to unnecessarily operate during injection of the refrigerant. Thus, it is possible to avoid such a situation that the injected refrigerant leaks into a suction pressure chamber and the quantity of circulation of the refrigerant cannot be sufficiently increased.
The scroll compressor according to the present invention preferably further comprises a discharge port (19) discharging the compressed refrigerant and a discharge valve (20) for opening/closing the discharge port (19) and preventing the refrigerant from counterflow.
In unloaded operation, the scroll compressor is generally operated at a low speed. Therefore, discharge resistance of the refrigerant is so reduced that the refrigerant may flow backward in the discharge port (19). Such counterflow of the refrigerant can be prevented and counterflow loss can be reduced by providing the discharge valve (20) in the aforementioned manner. Thus, efficiency in low-speed operation can be improved.
The scroll compressor according to the present invention preferably further comprises a relief port (29) communicating with the compression chamber (40) reaching the discharge pressure and a relief valve (31a) opening/closing the relief port (29).
The scroll compressor is operated at a high speed in an unloaded state under conditions of a high evaporating temperature, a low condensing temperature and large required refrigerating ability, for example. When the scroll compressor is operated at a high speed, however, the flow rate of discharge gas may be increased to increase over-compression loss. The refrigerant reaching the discharge pressure can-be properly discharged to a high-pressure space by providing the relief port (29) and the relief valve (31a) as described above. Thus, over-compression loss can be reduced and operating efficiency can be improved.
In the scroll compressor according to the present invention, the movable scroll (2) and the fixed scroll (1) preferably have spiral bodies (41, 42), and the tail end of one of the spiral bodies (41) preferably extends toward a portion close to the tail end of the other spiral body (42).
When the scroll compressor has the so-called asymmetrical spiral bodies as described above, unloading ports can be intensively provided on one portion as elements forming an unloading mechanism and injection ports can also be intensively provided on one portion as elements of a refrigerant injection mechanism.
The scroll compressor according to the present invention preferably comprises a suction pressure space (33) on the back surface of the fixed scroll (1).
When the suction pressure space (33) is provided on the back surface of the fixed scroll (2) as described above, no detour may be provided for releasing the refrigerant to a low-pressure space in unloaded operation but the unloading mechanism can be simplified.
An air conditioner according to the present invention comprises the aforementioned scroll compressor. Throughout the specification, the air conditioner is defined as including not only a cooling/heating system but also a refrigerator.
When the air conditioner comprises the scroll compressor having the aforementioned structure, high-efficiency operation is enabled in every operating state.
The air conditioner according to the present invention is preferably the so-called multiple air conditioner including a compressor (37) having a compression element compressing a refrigerant and a plurality of loading-side heat exchangers (25a, 25b, 25c) condensing or evaporating the refrigerant, and comprises a variable-speed motor, capacity control means (12a), an operating state detection part (39) and a control part (38). The variable-speed motor drives the compression element. The capacity control means (12a) supplies the refrigerant to the compression element or extracts the refrigerant from the compression element thereby controlling the capacity of the compressor. The operating state detection part (39) detects the operating state of the air conditioner. The control part (38) controls the operation of the capacity control means (12a) and the rotational frequency of the motor in response to the operating state detected by the operating state detection part (39). The aforementioned loading-side heat exchanger can be exemplified by an indoor unit (evaporator or condenser) of an air conditioner, for example.
When the air conditioner comprises the operating state detection part (39) as described above, the operating state of the air conditioner can be detected. The control part (38) can control the operation of the capacity control means (12a) and the rotational frequency of the motor on the basis of the result of the detected operating state. Thus, when the difference between an evaporating temperature and a condensing temperature is so small that high ability is necessary, for example, the control part (38) can operate the capacity control means (12a) for performing unloaded operation and rotating the motor at a high speed, thereby reducing over-compression loss. When the difference between the evaporating temperature and the condensing temperature is large and the ability may be small, the control part (38) can perform full-loaded operation without operating the capacity control means (12a) and rotate the motor at a low speed, thereby reducing counterflow loss (under-compression). Consequently, high-efficiency operation can be performed under every operating condition. In heating operation with a low outside air temperature and a low evaporating temperature, for example, the control part (38) can operate the capacity control means (12a) for injecting a gas refrigerant and rotate the motor at a high speed, thereby increasing the quantity of discharged refrigerant without extremely increasing the rotational frequency of the motor. In this case, reliability of the compressor can be improved. When adiabatic efficiency of the compressor is reduced and the temperature of the discharged refrigerant is increased in low-speed operation of the compressor, the control part (38) can operate the capacity control means (12a) for injecting a liquid refrigerant, thereby reducing the temperature of the discharged refrigerant. Thus, not only reduction of the life of the refrigerant or lubricating oil can be suppressed but also operation of the air conditioner may not be stopped due to an increased temperature of the discharged refrigerant.
In the air conditioner according to the present invention, the operating state detection part (39) preferably includes an operating pressure ratio detection part detecting an operating pressure ratio indicating the value of the ratio of a suction pressure for the refrigerant to a discharge pressure for the refrigerant in the aforementioned compressor and a required ability detection part detecting required ability of the loading-side heat exchangers (25a, 25b, 25c) in operation of the air conditioner, and the control part (38) preferably controls the operation of the capacity control means (12a) and the rotational frequency of the motor in response to the aforementioned operating pressure ratio and required ability.
Thus, high-efficiency operation can be performed as described above by detecting the operating state such as the operating pressure ratio or the required ability and controlling the operation of the capacity control means (12a) and the rotational frequency of the motor on the basis of the operating state.
In the air conditioner according to the present invention, the operating state detection part (39) includes a number detection part detecting the number of operated loading-side heat exchangers (25a, 25b, 25c), for controlling the operation of the capacity control means (12a) and the rotational frequency of the motor also in consideration of the number of the operated loading-side heat exchangers.
In the multiple air conditioner, the number of the operated loading-side heat exchangers (25a, 25b, 25c) also influences the required ability in addition to the relation between the evaporating temperature and the condensing temperature. When the aforementioned number detection part is provided, therefore, the operation of the capacity control means (12a) and the rotational frequency of the motor can be controlled also in consideration of the number of the operated loading-side heat exchangers. Thus, high-efficiency operation can be performed also when the temperature difference between the evaporating temperature and the condensing temperature is small and all loading-side heat exchangers (25a, 25b, 25c) are operated or the temperature difference is large and the loading-side heat exchangers are partially operated.